1. Field of the Invention
The present invention relates to an electric lamp unit for direct mounting. More specifically, the present invention relates to an electric lamp unit that can be mounted directly on a circuit board or other substrate, which may be used for disposing the electric lamp in a narrow space such as a control button of an audio system for a vehicle.
2. Background Art
FIGS. 3 and 4 show examples of such an electric lamp unit for direct mounting in the prior art. A direct-mounting electric lamp unit 90 shown in FIG. 3 comprises a micro electric lamp 91 and a color cap 92 for providing a desired color to the light emitted from the micro electric lamp 91. The color cap 92 has a bearing surface 92a by enlarging the outer diameter of the bottom portion of the color cap 92 or other means.
This direct-mounting electric lamp unit 90 is mounted on a circuit board 10 by inserting the lamp unit 90 into a mounting through hole 11 provided in the circuit board 10 from the backside of the circuit board 10, so that the bearing surface 92a of the color cap 92 contacts the circuit board 10, thereby the electric lamp unit 90 protrudes from the surface of the circuit board 10 by a predetermined height. In this state, lead wires 91a of the micro electric lamp 91 are soldered to the circuit board 10 to complete the mounting.
Another direct-mounting electric lamp unit 80 shown in FIG. 4 comprises a micro electric lamp 81, a color cap 82 and a holder 83 including a bearing surface 83a and a tube-like recess 83b for receiving the micro electric lamp 81 with the color cap 82. This direct-mounting electric lamp unit 80, in the same way as the above-mentioned electric lamp 90, is inserted into a mounting through hole 11 provided in the circuit board 10 from the backside of the circuit board 10, so that the bearing surface 83a contacts the circuit board 10. Thus, the electric lamp unit 80 protrudes from the surface of the circuit board 10 by a predetermined height. Then, lead wires 81a of the micro electric lamp 81 are soldered to the circuit board 10 to complete the mounting.
However, the direct-mounting electric lamps 90, 80 in the prior art mentioned above require soldering of the thin (e.g., 0.3 millimeters) lead wires 91a, 81a that are difficult to keep a desired figure, when the lamp units 90, 80 are mounted on the circuit board 10. The soldering process should be performed by hand, resulting in a problem of a low productivity in a whole assembling process of the circuit board 10 due to the mounting of the electric lamp units 90, 80.
Furthermore, in the direct-mounting electric lamp unit 90 shown in FIG. 3, the base portion of the micro electric lamp 91 is exposed when the electric lamp unit 90 is inserted into the mounting through hole 11 of the circuit board 10. Therefore, the electric lamp unit 90 is difficult to be mounted by an automatic insertion machine, for example, but should be mounted by handwork. As a result, the productivity is further lowered.
In addition, since the lead wires are soldered by handwork, a quality problem such that the micro electric lamp is fixed with slanting can be occurred when a pair of lead wires are applied with uneven tensions in the soldering process, for example.